From wood to bone

Regenerating bones with materials of natural origin that can bear a lot of weight might not be science-fiction anymore. Scientists are looking for new ways to transform complex and organized structures that already exist in nature into a device to improve bone and ligament substitution

The staggering similarities found with the bone brought the group of researchers working on the TEM-PLANT project to become the first one to use wood to develop organized and complex structures for tissue substitution and engineering. Both the bone and the wood are, in fact, hard, solid and living elements with holes in their inside. At the Institute of Science and Technology for Ceramics in Faenza, Italy, a piece of red oakwood is placed into a special oven so that it becomes charcoal. The charcoal is made of carbon molecules and the real bone is mainly made of calcium. With the right pressure, temperature and chemicals scientists can modify the molecules of the probe – one by one – changing an entire piece of charcoal to a calcium based probe. “We want this material to regenerate the bone within the body and at the same time to be load-bearing, something that until now can only be achieved through metallic bars”, points out Anna Tampieri, scientific co-ordinator of the project.

“The proposal of a biodegradable material which will allow to bear important loads is undoubtedly the most innovative aspect of this project”, says Elisabeth Engel, Senior researcher in the "Bio/non-bio interactions for regenerative medicine" group at the IBEC (Institut de Bioenginyeria de Catalunya).

The transformation from wood into a type of ceramic that is identical to the mineral part of the bone (hydroxyapatite, which makes up 80% of it) is completely “natural” from top to bottom, as there are no synthetic or hazardous by-products at any stage. “It is also a nano issue in the sense that we generate sub nanostructed material and that our verification system takes places below the nanometer”, Anna Tampieri says.

This ceramic material can be inserted into the gap of a fractured bone and stimulate the cells to wrap themselves around it and incorporate it (since they ‘recognize’ it as if it were an autologous bone), thereby forming new, healthy bone tissue. The implant will gradually disappear according to the amount of bone regenerated. Both researchers think that the material’s components do not have anything that might suggest possible rejections of the implant.

The TEM-PLANT technology is thought to suit particularly the regeneration of long bones, such as the tibia. At the moment, only about 20 sheep have received these bone replacements and they seem to respond very well”, Tampieri assures. “Now we have to strengthen the material from a mechanical point of view and have a broader and repeated number of animals”. Clinical trials on humans will start only once the new material has shown to be safe to implant. “What I do wonder is whether a device with a specific dimension is valid for surgeons, since not everyone has the same problem and they might prefer something more malleable that could be used in any clinical situation” Engel points out. “Besides, where we have more problems in regenerating bone is in older people, where also sex differences based on hormones are more relevant than in young ones. It is a source of debate whether this kind of regenerative medicine is to apply to them. I myself think it is definitely more suitable for young people”.

No one can predict when clinical trials will start, but it might take years before the first human receives a wooden bone implant.